You can indeed use the motor oil in the auto parts stores. I would use
something like Mobil 1 myself, but regual motor oil is really good enough.

My compressor is very lightly used, so I have yet to change the oil
on it in the last 3 years. I figured as soon as it started showing a
little bit of dirt or cloudiness, then it's time for a change.
However, on my next change, I wanted to use something that is the
really good stuff.

Anyone here knows whether using synthetic oil would be better or
worse than the normal oil on an air compressor?

Angello